Background: Physical inactivity and sedentary behaviour are known to be important risk factors for chronic diseases, but articles comparing prevalence in young people across countries are, especially for low and middle income countries, lacking.

Objective: To describe and compare levels of physical inactivity and sedentary behaviour in schoolchildren from 24 countries across four WHO Regions.

Methods: The analysis included 96,072 schoolchildren from 24 countries that participated in the Global School-based Student Health Survey (GSHS) and conducted data collection between January 2003 and May 2007. The physical activity module of the questionnaire included questions on overall physical activity, walking or biking to and from school and on time spent doing sitting activities.

Results: Alarmingly few students engaged in sufficient physical activity. In all countries, less than 2/3rds of the schoolchildren met public health recommendations, with the highest prevalence of inactivity in Egypt (90.8%, 95% CI: 86.8-94.8%) and the lowest in China (70.9%, 95% CI 67.8-73.9%). The prevalence of not walking or riding a bicycle to school ranged from 16.6% (95% CI: 10.2-22.9%) in China to 81.8% (95% CI: 79.5-84.2) in Cayman Islands. In more than half of the countries, over 1/3rd of the students spent three or more hours per day on sedentary activities, excluding the hours spent sitting at school and doing homework.

Conclusion: In all analysed countries, prevalence of physical inactivity was very high. The great majority of students did not meet public health recommendations. These findings require immediate action, and efforts should be made worldwide to increase levels of physical activity among schoolchildren.